High-resolution chromosome mapping will be used to identify and characterize genes which normally govern adult longevity in the nematode Caenorhabditis elegans. By studying the genetics of aging model organisms such as C. elegans, we hope to gain a better understanding of the genetic determinants of human aging, and the ability to prevent or ameliorate senescence-associated diseases. Recognizing that the genetic study if aging has been greatly impeded by the labor-intensity and variability of survival assays a new assay system is proposed to partially automate the monitoring of many survival cultures in parallel. Progress has also been made on several improvements in C. elegans genetic mapping : a 12 to 15-fold increase in the number of polymorphic markers available for chromosomal mapping, and a novel procedure for determining high-density genotypes in a single operation. Over 1000 recombinant-inbred (RI) lines will be generated from inter-strain crosses; al lines will then be assessed for lifespan, and the longest- and shortest-lived 10% of lines will be genotyped and their survivals reassessed. Such "selective genotyping" greatly increases the power of mapping procedures, per genotype evaluated. As an even more extreme application of selective genotyping, the high-density mapping assay is being scaled down for application to individual worms. Thus, a sample of the longest-lived 0.5-2% of individuals will be analyzed from large, heterogenous cultures comprising several thousand different RI lines, grown as a synchronously-aging cohort (Ebert et al., Genetics 135: 1003, 1993). Loci found to have significant effects on lifespan will also be tested for interaction with other sites. In order to further define the gene regions identified, congenic lines will be created for each significant locus, in an otherwise-homogenous ( and contrasting) genetic background; the implicated genes will thus be localized to the areas of overlap between multiple congenic lines. Candidate genes will be sought in the indicated regions, and will be examined for inter-strain polymorphism-as expected for genes implicated in inter-strain crosses. The novel procedures developed for polygene mapping may have broader applications, including utility in the Human Genome Project.